Lap



A. P. M ARTHUR LAP Feb. 13, 1945.

Fil ed Dec. 1, 1943 Law mm M Patented Feb. 13, 1945 1,; umrso STATES PATENT OFFICE 2,369,586; I i o n Aleirander P; McArthnr, Chicago, V i- Application December 1, 1943, Serial 1%. 512,455 I e olaims. (01. 51-1843) The process of lapping holes to finish them very accurately-for precision work, as usually practiced, is a slow and costly matter; it is necessary to-removethe laps from time to time to supply additional lapping compound; the laps frequently freeze'in the holes despite the most careful attention on the part of the workmen;

adjustmentto compensate for wear is difficult; and, where,a hole has a bottom, it is'diflicult to make a square 'cor'n'er" there because the lap-' ping 'compoundaccumulatesin the bottom of the hole and'soon wears away the corner of thelap andleaves it rounded. 1

The primary object of the present invention is to make possible rapid and accurate lappingofholes, thereby, greatly increasing output and greatlyreducing'costs. I

a In my endeavors to achieve my main object, I

conceived several novel features each of which in itself is an improvement over prior'practice' while, together, they overcome all of the aforesaid objections, as well as others;

' The various features of novelty whereby myinvention is characterized will hereinafter'be pointed out -with particularity in the claims: but, fora'full understanding ofmy invention and of its objects 'and advantages, reference may be had to the following detailed description taken in connection with the accompanying drawing,

whereina v Figurelis an elevational view of a lap'emj- 3 is asection' on line 3-3 of Fig. Lindicating,

as does'also Fig.2, a lapping compound'in' pocketsoutside of the lap; and Fig. 4 is a perspective view of the adjusting wedge. I

In the drawing Ihave illustrated a device containing'all of the novel features and for the sake ofbrevity, I shall describein detail only this" highly developed formyalthough it will be 'understood that each feature in itself improves the ordinary lap. The lap is composed ofa body member I, a shank2 and a wedge block 3. The

body member is made from a solid cylindrical block of any suit'ablemetal. The shankis'preferably screwed on so that it maybe applied to A central slot 4 ex-:

that forms a continuation thereof. These two This slot slots transform the body member into a heavy hairpin whose two legs 6 and I have a spring.

down throughthe upper end of the body member.

The slots 8 lie in planesthat are on opposite sides of and parallel to the plane of the slot 4 and they extend down far enough to'overlap' the upper end o f'the slot 4. Thus there are formed at "the upper 'endfof the body member lips or legs 9 and "Ill lighter than and extending in the opposite direction from the legs 6 and 1, respec tively The body member is mutilated peripherally in those areas where the slots open out, pref-. erably by flattening, as indicated at H, sothat when the body" member is inserted in a hole A inapiece of work B, the cylindrical wall bounding the hole .forms ,withthe body member a pair, of substantial pockets ,0, extending throughout thellength of thelatter. In the periphery of the bodymember are two, d'ee'p channels I2 each of which extends from thelower end of one of the flattened areas to the upper end of the other such area, The, two channels are inclined in the same usual or suitable way. "The lapping compound; D may be applied, to-the lap either before or after, it is attached to the ,machine. any event, after -thelap, carrying its charge of com pound, is inserted in the'hole to be lapped and is rotated at high speed, the compound is driven. out into the pockets C through centrifugal action. Inthis way-the compound is applied positively. to thesurface to ,be'lapped, and need only;

be rubbed against such surface by the revolving lap.

The heat generated by the lapping action soon causes the compound to become very fluid, so that it runs downward in the pockets. However, instead of being left free to escape, the compound is picked up by the channels'and is forced up the same until it is discharged into the upper ends of the pockets. In order to secure this result it is of course, necessary that the. lap berotated in the directionithatzmaltea the Iowen en'dsaoffthe channels the advance ends. It will be seen that not only do the channels cause the lapping com.- pound to be recirculated through the pockets, but they also act as distributing means that leavea coating of compound on the surface thatis being lapped as the streams of compound" travel. upwardly and laterally along; the channeistwhil'e. in contact with said surface.

The mutilation of the cylindrical surface of thelap to? provide areas: of... considerable angular. width. extending throughout the length of: the: body memb'en oi the; serves. another useflili urpose. AIL Iapsi that; I. have: heretofore. used-frequently freeze in therwork, causingelosss 05 time: and creating. the danger. that the. work wills be: spoiled... The presenceeofi the idle zones on the-lapgives every pa-rt' of thesurface in the piece on work. a: breathing. spell; as itwere; twice in: each: revolution: of the lap. Whateven the teason thenetor may be the. fact-ia that. with my improved. lap freezing of same: in. the. hole. is: eliminated-.. v

Initial adjustment or compensation. for wear may be maria. as before stated, by'simply tap-- ping-1 the wedge. until the lower end ot. the lap has-expanded sufllciently. Thisoperatiom causes. the free; ends; ofthe. lighter. legs on lips 9- and In to approach each. other; contracting the. upper end. of. the. body memben. But,v when. the lower. ends. of the legs 6 and. 1. are. pressed: together: to. enter thalap ina hol the two. legs. on each sideact-as abeam which rocks about the wedge. as. a..fulcrum,. thereby causing the. free ends. of the; legs 9 and-Ill to swing apart. and" to press. against the surrounding. wall when the. lap is pushed; all' theway d'own.

There aretwo factorswhichmakeit practicable tolap sharp corners at the. bottom of. a. hole- In first place, compound. cannot. collect. in. the.

become slightly rounded, the sharpness thereot can easily be restored by simply grinding; a little" offtheflatbott'om of the lap; The; nature-of the lap is such that its efficiency will not be diminished by'a few of such grindings".

A further valuable characteristic of my lapis that it may be made ina comparatively few sizes extending over a wide range, while any' inter-' mediate micrometer size may then be obtained. by trimming down' the nearest" I'argersi'ze: Thus, forexample a; $5 lap maybecutldown'; as much ae: ""withoutf interferingwith the proper work:- i'ng of the channels or" detracting from the. efiectiveness of" the spring; elementsof the device. The larger" the lap the greater the amount of" reduction can be made in the. diameter to prodime a wanted size; Thus a 2 lap may be 'cuti down as much as 1%"; if necessary.

I. claim? lL Ai tooi ofthe character described; comprisof longitudinal peripheral areas mutilated to form with a surrounding cylindrical wall in a piece of work a plurality of long longitudinal pockets, and having, also, a diagonal peripheral uninterrupted channel leading from the lower end of at least one of said areas to another at a point well above the lower end of the latter, so as to 20 each of said areas to the other area at a point ing a cylindrical body member-having: ax plurality in well. above the; lower: enct. of. the; latter area; so that; each.- ot. said channel's communicates; with. bothof said. pockets at. points; within the length at the body member, said channels being; biased. in the same. direction so as. to. cause. each. con,- tinually to feed lapping-rcompoundztrom the lower end of one. pccket into the other pocket; while said member revolves during, a. lapping; operation.-

3=. tool of the: character; described compris.-- ing a. cylindrical-body member diametrie cally opposed longitudinal; areas' lflattened to-form with a-jsurrounding'i cylindrical wall. in. a piece; of work a pair of long longitudinalpockets and.- having. also, av diagonaia peripheral: channel leadtrom. each of. saidlarean; to theother,-; all: of. said channels being; biasect in. the same: direction: so as to cause each to convey lapping; compound: from: one pocket. toa higher point. in. the other pocket while. said. member; revolves: during" a. lap-- ping;- operation.

4;. A toolofthe. character d'escrilied comprising" a cylindrical body member audeepi slot ex:- tending; upwardly through. therbottom. and across a. diameter;- of" said member thee periphery" oisaid member being: cut away-along longitudinal lines beside said; slot.-

form; withv the: surround ing wall of aupi'ece of; work; pockets; of. substantial; extending: lengthwise ofi saidl member; and communicating with: said; slot, said: member 3 having, also, peripheral diagonal channelseaclr extending; from the'lowenendi of one; off the pocket-forming regionatm the; upper end or? the.- other such region; all. or. the: channels being; inclined inthe same direction.

5 A took on the character: described comprising; a. cylindrical. body member-having; adeep. slot extending upwardly through the: bottom andacross a. diameter of! said. member;v the peripheryperipheral diagpnalichannels. all; extendingv imthe:

same direction fmnnthe; lower mdcofi one'ofsaid: fiat faces. to the: upperend, of; the-other flat. face.

6 A took 01' the. character descni'bed; comprise ing a cylindrical. body havi'nsf. a.- deep: slot: extend-- ing; upwardly through the bottom and. across. a. diameterwof said memhen, the; of said.

member being cut away along: longitudinal lines beside; said. slot: to formwiththe-surroundin W of a piece or; work; at; least, one: packet. extending; lengthwise. of. member and. communicating:

with the slot, and said member having, also, other slots entering the upper end of said member in planes parallel to and on opposite sides of the plane of the central slot and being deepjenough to extend down past the upper end of the latter slot.

7. A tool of the character described, comprising a cylindrical body having a deep central slot extending upwardly through the bottom 'and across a diameter, the periphery of said member and a Wedge slidable in said central slot and par tially entered in the said narrower slot.

8. A tool of the-character described, comprisinga cylindrical body of spring metal having a deep central slot extending upwardly throughthe bottom and across a diameter, said member being flattened on opposite sides along said slot to form with the surrounding cylindrical wall of a piece ;of work pockets extending lengthwise of said 5 member and communicating with said slot, the

central slot merging at its upper end into a narrower slot that forms a continuation thereof; said member having, also, two other-slots entering through the upper end thereof and arranged in planes parallel to and on opposite sides of the central slot and being deep enough to extend down past the juncture of the central slot and the said narrower slot to produce spring lips at the upper end of said member; and .a wedge slid- I able in said central slot and partially entered in said narrower slot to exert a, pressure tending to spread the lower part of said member and to serve as a fulcrum to cause the free ends of said lips to swing outwardly when the lower end is contracted to enter a hole to be lapped.

v 9. A device as described in claim 8 in which there are also peripheral channels in said member biased in the sam'direction and each'lead- I ing from the lower end of one flattened area to the upper end of the other such area.

I ALEXANDER P. MCARTHUR. 

